1. Field of the Invention
The present invention relates generally to hybrid waterbed mattresses including in a single envelope a bladder and foam softsides providing lateral support for the bladder.
2. Discussion of the Prior Art
Hybrid watermattresses typically include a waterbladder which is disposed centrally of the mattress, and a plurality of sidewalls typically formed of a resilient grade foam material which surround the bladder at the lateral edges of the mattress. These sidewalls are commonly referred to as "softsides". It is the purpose of the softsides not only to provide lateral support for the bladder but also to provide a more conventional surface on which one can sit at the edge of the mattress. A quilted ticking provides an envelope which encloses both the bladder and the softsides. This construction forms a hybrid watermattress having substantially the same appearance as the more conventional innerspring mattress, while affording the luxury of a flotation sleeping surface.
In the past, softsides have been constructed with generally flat surfaces facing the mattress bladder. These surfaces have been designed to complement the manufactured shape of the bladder but have failed to appreciate that the shape of the bladder in normal use changes drastically. For example, the lateral surface of a bladder which is manufactured to be vertical achieves an arcuate shape when it is filled with water. In general, all flat shapes of the bladder will tend to balloon under the pressure of the water within the water cavity.
Attempts to support these ballooning arcuate surfaces with the flat surface of the softsides has created uneven pressures on the material of the bladder. Representative of this prior art is the watermattress disclosed in U.S. Pat. No. 4,571,762. The greatest pressures have tended to locate in the areas of the seams and thereby developed points of weakness for the bladder.
Of course one of the greatest concerns in any mattress having a water filled bladder is the integrity of that container. If even a pinhole develops at the seam or any other location, large volumes of water can be released into the surrounding area. Thus the watermattress industry is always interested in reducing the stress on the seams of the bladder.